Hi there,
I have just gutted my Sovereign and need to replace the floor. Preferably I would like to keep the shell on. I'm working with limited tools and out in the garden, mostly by myself.
Is there a step by step guide to doing it?
I would like to replace the floor with hardwood (or pine) tongue and groove floorboards, with no additional subfloor. Thought about adding some more wooden joists between the metal floor frame.
Has that been done before?
Can I work in sections, pulling out the rotten plywood and replacing with floorboards under the wall frames?
Thanks for any ideas and experiences/guidance.
Cheers,
Germanaussie

No response. Not sure if that means that my plans are unrealistic? After thinking more about it, do you think it would work to do a slow exchange of floor around the wall frame. Take a bit of the old floor out, maybe 2 feet along the edge or so at a time, then insert and bolt into place a fitting length of hardwood floorboard, so that the frame is stable on the floor again, then take out all the rest of the old floor, (check for any work needed to the underneath), then insert wooden joists between all the metal ones (by attaching them under the outer circle floorboards, then adding in the rest of the floorboards, nailing them into the wooden joists like house-floorboards and resting them on the alternating metal joists.
Is that how a frame-on floor make-over works?
Thanks for any input,
Germanaussie

There are several threads talking about the process, though maybe not to the detail of a step-by-step "how-to" tutorial. You might search for "shell off" "shell on" and "floor replacement."

If I were to break it out, it would look like this:

1) Drill out the rivets that attach the bellypan/banana wraps to the shell
2) Ensure that all rivets holding the shell to the C-channels are removed (depending on whether the C channel will come with the shell or remain on the floor.
3) Remove the entire interior furnishings, and the lower interior skins to gain access to the various bolts that hold the C-channel to the floor/frame.
4) Build some gantry lifting frames (see link below)
5) Lift the shell, and pull the trailer frame out from underneath
6) Remove old, rotten floor sections from the frame, but save them for use as a template.
7) Secure the shell, then use the gantry lifting frames to flip the trailer frame
8) Remove the bellypan, saving the sections either for reuse or as templates for replacement. Also remove and discard the old, sagged out axles.
9) Use the gantry frames to suspend, flip, etc., the trailer frame while you are repairing it, knocking the rust off of it, and painting it with POR-15
10) Flip the frame upright again, and install your new plywood subfloor (more discussion on this shortly).
11) Flip again, and install the insulation under the floor. Now would be a good time to install grey tanks too, if that is your plan (and it might as well be).
12) Reinstall the bellypan.
13) Install your new axles.
14) Flip the frame again, put the wheels on.
15) Position the gantry frames over the shell and lift it again. Roll the frame back underneath and drop the shell into position.
16) Rivet the shell to the C-channels, bolt the C-channels to the frame/subfloor
17) Decide what to do with the rodent infestation in the insulation in your lower walls.

Now, for the various questions/concerns you had regarding your plan.

1) Space: I did a shell-off in one lane of my driveway. After landing the shell, I commandeered my open patio area to do the frame work. I have postage stamp sized yard. I realize my trailer is shorter than yours, but you really don't need an acre of land to do a proper shell-off.

2) Working by yourself: About the only task where you absolutely need assistance is with the buck riveting of the shell back together, and the installation of the bolts that go through the c-channel, floor, and frame. So if you can get some help for one day, you can do pretty much everything else on your own.

3) Floor design: The subfloor is a part of the structure of the semi-monocoque design of the Airstream. As such, you want it to be in as big of pieces as possibly (for structural continuity), and you want it CLAMPED between the shell and the frame. The absolute best way to accomplish all of this is to completely remove the shell, install the new subfloor, and put the shell back on. I have read a few threads describing peoples' efforts to replace their floors with the shell on, and my conclusion is that they work twice as hard, and get arguably marginal results for their troubles. Adding a bunch of wooden floor joists to support your floor-board design is counter productive. You will add a whole bunch of unnecessary weight and fill up the bays in your frame that you should be keeping clear for tank and plumbing installation. Plus, loose floor boards, nailed to joist, are just not likely to hold together after a few miles of the whole structure twisting and vibrating. Have a look at the pictures of frames in the link below, and you will see what you are up against. The subfloor bolts to the outriggers, and they are few and far between.

Have a look at the following thread--it shows the design of the lifting gantry frames and what you can do with them. Post 9 and 11 show some good pics of what can be done with the gantry frames. There is also a diagram for building the frames in a pdf at the end.

Thanks so much for your input!
This made me re-think everything!
I don't think I can re-do the floor after all. It's just too much work that I don't feel qualified to do. Parts of the floor definitely need replacing but other parts are still okay I think. I hope the frame/trailer underneath is good enough also, looks rusty from what I can see but not as damaged and rusted through as in some of those pictures!
If I need plywood underflooring anyway I might as well leave the sound bits in place and just repair. Put a floating floor over it and be done! If the frame underneath gets the okay!

You do not have to accomplish an entire "shell off" restoration.
It's very difficult for anyone to give recommendations without truly "seeing" the extent of your current damage. Fixing a current subfloor problem with "floating floor" over the top of it, is probably not going to work very well. Do a bit of legwork, evaluate what you REALLY MUST FIX and then ask for assistance *take lots of pictures, too*).
Plan on your project to take twice as long as you think and cost three times your initial estimate (i.e. Your rear floor needs replacing, but once you remove the bad scraps you realize the toilet base might as well be redone, etc).
Here's a BIG tip: If your floor needs replacing, you MUST identify the root cause (there are probably multiple roof/window leaks), to limit it happening again.
Good luck and we're looking forward to your progress.
Ruck

cut out bad sections of the floor and look underneath at the frame. If it is rusted beyond surface rust, you can do some repairs, but you may need to pull off the belly pan to get them done. If the rust is not severe, you can sand and paint the frame.
Then add in sections of plywood to replace the rotted areas of subfloor. A wood hardener can be used to strengthen other areas that are weaker but not rotted badly. I did this under the refrigerator area of my 66 trailer, it was the only really rotted area of the floor . I sealed the mildly rusted frame with bondo and painted it. It was solid as a rock when done.

When done I would epoxy around the edges of the whole floor, and cover it with your choice of material. I used cork

How about a few pictures of your floor? It could be that it isn't so bad that it can't be patched instead of replacing it altogether. I tend to be one of those "as long as I am here..." kind of people, and I suppose that is why I have been working on my renovation for 3 years, and still have a lot of work to do.

Yes, that is my plan. I will go out this weekend and make a video of the whole condition, of floor, underneath and walls.
This discussion has been so helpful. I now know that my plan of just floorboards will not work and Genesis (nontoxic sealed) bamboo floating flooring on the plywood sub-floor is my next choice. Unless you guys think it will make the whole floor too heavy.
I will not put a bathroom in anymore. Just a big bed in rear section,then a wardrobe and compost toilet cubicle on each side, then a long kitchen bench on the door side of trailer with fridge, pot belly stove and some storage on the opposite long wall. Then a sofa-bed and table with side seating in the front of the AS.
I want as little plumbing as possible, same as with wiring.
The space where the toilet black water tank was I could maybe use for storage (like a drawer accessible from the outside?). Please tell me straight if any of my ideas are totally unrealistic!
I really hope that the underneath rust is just on surface. Will show you video soon...
Thanks for all your input!
Germanaussie